Strain-Dependent and Site-Specific Differences in Irinotecan-Induced Skin Pigmentation in Mice

Area of Science:

• Pharmacology
• Dermatology
• Genetics

Background:

• Irinotecan is an anticancer drug known to cause skin pigmentation.
• Differences in irinotecan-induced skin pigmentation across mouse strains and specific skin sites are not well understood.
• Investigating these variations is crucial for understanding drug side effects.

Purpose of the Study:

• To compare melanocyte activation in plantar and genital skin after irinotecan administration across three different mouse strains.
• To investigate strain-dependent and skin site-specific variations in irinotecan-induced pigmentation.
• To explore the regulatory pathways involved in drug-induced melanocyte activation.

Main Methods:

• Repeated administration of irinotecan to ICR, C57BL/6, and C3H mouse strains.
• Assessment of melanocyte activation using 3,4-dihydroxyphenylalanine (DOPA) staining.
• Immunofluorescence staining for microphthalmia-associated transcription factor (MITF) to evaluate melanocyte activity.

Main Results:

• No macroscopic pigmentation was observed, but DOPA staining showed increased melanocyte activation in plantar skin of all strains.
• Genital skin showed strain-dependent differences: ICR and C57BL/6 mice had DOPA-positive cells, while C3H mice did not.
• MITF staining results correlated with DOPA staining, indicating enhanced melanocyte activation in affected areas.
• DOPA-positive cells were found in the genital skin of albino ICR mice, suggesting activation independent of melanin production.

Conclusions:

• Irinotecan induces melanocyte activation with significant strain-dependent and skin site-specific variations in mice.
• Melanocyte activation by irinotecan may involve regulatory pathways independent of intrinsic melanin production.
• These findings highlight the heterogeneity of drug-induced skin pigmentation and inform future research on irinotecan side effects.